In the 2nd half, the team of divers face that the Arcadia ship was sunk on purpose and why it felt alive and moving. There were reasons that the ship was not explored and it was only realized when they faced what the ship had been showing. This book is closely tied to subtle and descriptive horror that does not have too much action. The theme is ignorance since they do not 100% know each other's true self as they also ignore signs of the abnormal.